Chapter 13 Emotions

emotional expressions act as prosthetic telepathy, they send out clear and unambiguous signals about otherwise unavailable internal states

fear, anger, surprise, happiness, sadness, disgust

• it is not the feeling of an emotion that causes the body's reactions, but it is the body's reaction that causes the emotion
• body first then emotion afterwards
• bottom up theory

• total surgical separation of visceral organs from the brain does not abolish emotional behaviour
• physiological responses are too nonspecific to signal a single emotional state
• many bodily responses are slow, on the order of mins but emotions occur at a much faster time scale 
• artificially inducing bodily responses isn't enough to generate subjective emotional states

• top-down theory 
• sensory info relayed through the thalamus is routed to two pathways
• one to the hypothalamus which coordinates the physiological response in the body (primitive response) 
• one to the cortex, which controls the expression of emotional responses (top-down control over primitive reponse)

• emotional states arise from a synthesis of the bodily physiological reactiosn detected by the brain (bottom up factors) and the cognitive context under which the brain interprets these sensations (top down)
• supported by studies that manipulate physiological factors and cognitive factors to see how their interaction influences emotion

• can be associated with different emotions 
• e.g. epi with knowledge vs epi without knowledge = mild emotional response vs strong angry response

• brain's role is complex
• high order areas in the cerebral cortex use info from multiple sensory modalities to interpret the world and react to it 
• areas in the limbic system, ventral striatum, and insula are important for the coordination of physiological reponses linked to emotion, the feeling of emotions, and emotional memory

• an interconnected set of regions is important for emotional experience
• coordinate physiological and behavioural responses to emotional stimuli

• the hypothalamus is critical for many functions essential for survival including homeostatic function, attack and defence functions, and reproduction
• also causes changes in one's internal state, which is part of emotional experience

• 1. autonomic pathways: stimulates sympathetic and parasympathetic nervous systems
• neuroendocrine pathway: controls the activity of endocrine glands, which release hormones 
• 3. motivational pathway: organises goal-directed behaviour with help from cerebral cortex

• subjective emotional experiences seem to emerge at this level of the hierarchy, and not earlier 
• hypothalamic tumours can cause overeating, fits of laughter, fits of inappropriate rage, depression
• DBS of ventromedial hypothalamus can cause panic attack, nausea, and subjective anxiety

• receives visual, auditory, olfactory inputs from the thalamus and cortex as well as some interoceptive info from the brainstem 
• sends output to somatic and autonomic nuclei in the brainstem to hypothalamic nuclei, and to the striatum and cortex 
• has similar output functions as hypothalamus, but mostly gathers info from the external as opposed to internal world

• basolateral amygdala - figure out what things are worth, track value and emotional significance by drawing on different sensory modalities
• centromedial amygdala: figures out what has to be done. controls hypothalamus and brainstem; draw on external sensory info to modulate internal drives and hormonal functions

• important for detecting threats and implementing fear response (fear conditioning)
• slide 21

• amygdala neurons can learn the reward value of a stimulus
• amygdala neurons can also adjust their responses to reward based on the animal's internal state

results after removal of amygala, includes inappropriate motivational responses such as hyperorality, hypersexuality,  constant masturbation, and indiscriminate copulation(including objects or other species)

• a rare illness associated with destructive lesions in the amygdala
• interacts general intelligence, memory, language, perceptual functions, but severe impairment in the ability to experience or recognise fear

• the hippocampus is involved in episodic memory and spatial navigation and is also important for emotional memories
• not unrelated functions -- episodic memories occur in a particular spatial location; we can use memory to navigate and both memories and navigation can stimulate emotions

• stimulation of the medial forebrain bundle causes release of dopamine in the ventral striatum
• aka pleasure centre of the brain by media
• damage in the vicinity can produce severe depression and anhedonia

insula important for the subjective, sensory experience of emotions, the bodily feelings of emotional states

• important for the generation of gut feelings
• Phineas Gage

• serve different roles
• anterior: complex internal sensations or feeligns such as anger, sadness, elation, disgust, sexual arousal, anxeity 
• posterior: basic visceral sensations such as pain, temperature, fatigue, itch, pressure, and tension

damage to vmPFC seems to impair performance on tasks that depend on gut feelings and ability to foresee the emotional consequences of one's behaviour

• measures emotional responses by looking at the changes in the electrical resistance of the skin 
• healthy individuals generate galvanic skin responses when they contemplate drawing from the risky decks as if anticipating the emotional outcome to follow 
• vmPFC legions generate reduced galvanic skin responses in anticipation of risky choice but do see response after outcome are revealed

emotinal states can direct behaviour by generating internal bodily states called somatic markers. These can be used to guide decision making under uncertainty when external cues aren't available to guide behaviour

cmPFC plays a key role in driving autonomic, neuroendocrine, and visceral signals in response to myriad sensory inputs that convey info about the world

• for emotions to be context sensitive, the brain has to access info about current behaviour, current goals, expectations, memoris, and the meaning of what you see in front of you
• emotional reappraisal: adjustment of emotional responses to outside stimuli based on context
• important: we can't change what happened to us, but we can change how we think about it

• brain activity associated with attempting to decrease emotional reactions 
• amygdala, vmPFC, vlPFC
• successful reappraisal of negative emotional images is associated with up regulation of the nucleus accumbens and down regulations of the amygdala

NT systems influence emotions but this can only happen through effects on neurons, which neurons they target and how those neurons response

• central to mood regulation and even temporary changes in serotonin can have measurable effects on emotions
• increased serotonin may help shift mood by affecting how the cortex appraises the situation: it doesn't erase sad moods, but changes biases in interpretation from negative to positive
• tangent: there are over a dozen receptors distributed differently throughout the brain with own effects on neural activity and emotion

• many antidepressant medications act on norepinephrine
• norepinephrine agonists alleviate symptoms of depression, nudging emotional biases away from  negative and towards positive

• main inhibitory NT in the nervous system 
• one function is to control anxiety, agitation, aggression and thus medication often targets GABAergic system

• class of medication that act as GABa agonists throughout the body
• high doses produce coma-like unconsciousness and anaesthesia
• low doses produces sedation, relaxation, and have anxiolytic effects
• reduces anticipatory anxiety and in turn correlated with reduced activity in the anterior cingulate cortex and anterior insula

• substance in and of itself is not mood altering 
• whether a substance hs an effect on mood depends on whether it can and to affect receptors in part of the brain involved in generating and modulating emotions